diff --git a/backend/app/api/files.py b/backend/app/api/files.py
index a074615..da64e07 100644
--- a/backend/app/api/files.py
+++ b/backend/app/api/files.py
@@ -283,8 +283,11 @@ def download_file(file_id):
     if not filepath.exists():
         return jsonify({'error': 'Datei auf Datentraeger nicht gefunden'}), 404
 
-    return send_file(str(filepath), mimetype=f.mime_type, as_attachment=True,
-                     download_name=f.name)
+    # inline=1 renders the file in-browser (used by PDF/image previews).
+    # Default is attachment so normal download buttons still save to disk.
+    inline = request.args.get('inline', '0') == '1'
+    return send_file(str(filepath), mimetype=f.mime_type,
+                     as_attachment=not inline, download_name=f.name)
 
 
 def _download_folder_as_zip(folder):
diff --git a/frontend/src/views/PreviewView.vue b/frontend/src/views/PreviewView.vue
index 0f7005a..6f01f11 100644
--- a/frontend/src/views/PreviewView.vue
+++ b/frontend/src/views/PreviewView.vue
@@ -157,7 +157,7 @@ async function loadPreview() {
     previewType.value = data.type
 
     if (data.type === 'pdf' || data.type === 'image') {
-      previewUrl.value = getTokenUrl(`/api/files/${fileId}/download`)
+      previewUrl.value = getTokenUrl(`/api/files/${fileId}/download?inline=1`)
       canEdit.value = false
     } else if (data.type === 'html') {
       htmlContent.value = data.content